Spectrum Roentgen Gamma (SRG, launched in 2019) hosts the eROSITA instrument, a set of seven co-aligned soft X-ray telescopes covering the 0.2-10 keV band, with a field of view of 1\(^\circ \)  and \(\sim \) 15\(^{\prime \prime }\)  spatial resolution equipped with CCDs with spectral resolution of 60-80 eV in the 0.5-2 keV band [1]}. At the end of 2023, after four years surveying the whole sky once every 6 months, eROSITA will build up an all-sky survey 25 \(\times \)  deeper than RASS in the 0.5-2 keV band [2]}, [1]}.
